Simon Chambers

Posted by Paul Marsh on 10/01/2014 13:57:01: There's a van round the corner, where the tax ran out last July! https://www.gov.uk/report-untaxed-vehicle Edited By Simon Chambers on 10/01/2014 20:55:56

BBC has a new video online, showing the latest work restoring the Dornier. **LINK** Personally I think its great that its happening. What many people don't realise is that there isn't plans or engineering drawings of most of these aircraft. These were destroyed either during the war (bombing, etc) or after the war when the type becomes obsolete (when people don't appreciate the historic significance of the aircraft as it was so soon). So building a replica is almost impossible without something to compare against. I remember a colleague who worked at a aero trust telling me that for a long time the Bristol Beaufort blue prints were missing. They were hidden during the war to prevent them being damaged - but no-one really knew where they were put. Anyway when a major restoration happened of one of the original design offices, they were found hidden up in the roof. Unfortunately the wax lined tubes that they were stored in had failed, so after 40-50 years of elements leaking onto them they were mouldy mush. I have no evidence either way of the Dornier, but I imagine its probably a similar scenario that all the original design drawings are long gone. Si.

That looks perfectly safe and reliable. Very tempting to get one to strap to something...

Include me please Si

I'm waiting for the multi-part serialisation in RCM&E named "The things you didn't know about where your planes come from and the hidden secrets about Chinese resellers by Scott Cupello"...

It's affectionally known as the Tubby FW190 on the American Forums... Long thread on it here: **LINK** Si.

I have ten fingers+thumbs - so metric makes much more sense to me!! Maybe imperial was more useful in an age when you might have lost a couple of widgets in industrial accidents... I still can never remember how many inches to a foot, oz's to a pound, feet to a mile - gah all different and inconsistent! It's something the editors should certainly think about putting both units on the plans - as the majority of the world is finally moving over to metric (even a lot of American engineering firms now are/have moved over). Si.

Incidentally the discharge curve of NiMh packs has the same 'fall off the cliff' style drop at the end like LiFe packs do. Given that there is only around 100mV of difference in pack resting voltage between 5% and 85%, again you can't accurately gauge the charge level of a NiMh pack based on voltage alone. In fact, most of these so called battery life remaining checkers only have around 25mV accuracy anyway. You really don't want to be in the air when the pack hits 1v per cell! I reckon the majority of receiver 'brown-out' problems are caused by receiver packs that are almost flat. Draw a 5A load (easily achievable with most modern servos) when 1.8Ah have been consumed, it'll go from 1.2v a cell to 0.8v a cell - 3.2v for a 4 cell pack. A lot of receivers operating on 3.2v will brown-out and then reset. Si.

Posted by Frank Skilbeck on 14/12/2013 14:53:42: the life pack voltage is and as this is like a Lipo the resting volts are proportional to the % mah left. Becareful, the discharge curve of LiFe packs is very different to LiPo. LiPo as you say will drop the voltage fairly proportionally as pack depletes. However LiFe packs have a dead flat discharge curve - so voltage alone is not accurate on remaining charge. So between 5% and 85% discharged, you're looking at less than <.1v per cell difference. So if you check your pack before you fly, it could be just as easily 85% discharged as 5% discharged. Obviously taking off at 85% used could be a very different flight from 5% used... This makes telemetry even more useful, as if the voltage starts dropping, you know you're at around 90% discharged and need to land immediately. However the flat discharge curve does mean that the servos will operate (speed and torque) in the same manner whether the pack is fully charged or part discharged - especially important and useful characteristic for acrobatics. Also the very low self discharge means that the pack will stay fully charged and given they are lighter than the equivalent ​NiMh packs, you can fit a larger pack in the first place (having more flight capability and negating the discharge problem above). Si.

Delta peak charging is ok if the algorithm in the charger is good. However most chargers they are not! The other problem with using Delta Peak is that it doesn't balance the cells. Like LiPos, NiMh packs can become unbalanced. As there is no balance port, the usual way of balancing a NiMh is deliberately overcharging them. When a cell is fully charged, it'll dissipate the excess energy as heat (hence why the get hot as they're almost fully charged). However this must not be done at a too high a rate that the cells can't sink the heat. Charging at 0.1C, most cells can dissipate this heat almost indefinitely. Note, I have seen that eneloop type cells don't like being overcharged constantly at 0.1C and it damages them. Personally, I don't use NiMh any more. My T8J and all my (glow) models now use LiFe packs. These have: Almost zero self discharge - so always ready to go) Can be safely fast charged - for when you forget to charge them, so you can do it at the field Lighter for the equivalent capacity - so you can fit a bigger pack and never worry about the pack going flat in a day Perfectly safe chemistry - they won't catch fire if overcharged, punctured or flattened. So you can safely install them tucked away in a model. Flat discharge curve - servos will respond with the same speed and force no matter how much left in the pack. Note that this something you have to watch out for, as you can't tell if a pack is flat on voltage alone. Equivalent to 5 cell NiMh pack - Once you've taken the top off the voltage (which is lower than a fully charged 5 cell NiMh pack), they'll give a nearly constant 6.6v Higher current draw - high current servos (actually a lot of modern servos are now much higher current than old ones) won't make the voltage sag. So again the servos response will be the same as the battery discharges. However also, it means there is far less risk of voltage Brown-Out on the receiver Cheaper!! Kinda a no-brain'er really.  In my T8J I use this pack - **LINK** At 1100mAh, is pretty much the same capacity wise as the original stock pack and it fits nicely in the back of the transmitter. Unlike the picture on HobbyKing, my pack came with 2 servo type connectors, so it fitted straight in without any soldering/crimping! For Charging, I just use my normal LiPo charge BUT set onto the LiFe charge mode. Si. Edited By Simon Chambers on 13/12/2013 12:24:18

Posted by Vecchio Austriaco on 11/12/2013 21:22:11: don't really like it from health and safety point of view. If the rope jams the heli is down... VA They can flick a switch and the line is released! Moving trees around by helicopter is widely done in the states and Canada. It's been going on for years. One of my friends brothers cut his teeth on helicopters in Canada with tree logging. Problem is, Helicopter time is so expensive, that it has to be done quickly otherwise it can turn from saving money to a massive loss making operation. Doing things quickly, especially with aviation, doesn't necessarily lend to the safest practices though. As you imagine, accidents aren't uncommon. I wonder how long it will be before this type of thing is replaced by a swarm of quadcopters! Si.

The 8J charger is a fast charger with built-in Delta Peak cut off. So even though it charges at a faster rate, as it knows when to turn off automatically its perfectly safe charging at the faster rate. NiMh will get warm as they are nearly charged and its perfectly normal for this to happen. They should be only getting warm, not hot/too hot to touch though! Si.

When my last subscription ended earlier this year, I never received any reminder at all. Not sure why I received nothing (no email and no letter), but never it did mean that I never got around to renewing it...!

What about a 7-series/S-class/A8? Not too much difference in second hand price and running costs aren't that dissimilar. However much higher spec and more prestige. I'd avoid the 2L diesel on the 5-series, this has a lot of problems with its timing chain which is expensive to replace and often causes catastrophic (expensive) failure. A well known common problem that BMW refuses to admit is common place nor a design defect (an unfortunately common BMW attitude with common faults). In fact I'd be cautious of any modern diesel - DMF failures are not uncommon and expensive, DPF again expensive when they go wrong (also may have been removed, which will become a MOT failure) and all sorts of other valves and high pressure gubbins that write-off any fuel saving you've made if they go wrong. Petrol models on the other hand are pretty fuel efficient nowadays and a naturally aspirated petrol engine is relatively simple to fix with little that can go wrong. Some models have more problems with their engines than others, so some research online is in order. For example, the 3l TDI A6's of that vintage are one of the few that don't have a dreaded DPF fitted as standard and generally a very solid, reliable engine. Finally, what ever marque you go for, make sure you have a good independent garage (i.e. non-main dealer) that has all the diagnostic tools to do any work on these cars. Pretty much any repair work done on these type of cars require manufacturer specific diagnostic tools. Si.

I did see your engine the other day and did see its going for a bit of a bargain at the moment!

I would point out though, due to the low frequencies involved, its pretty easy to design and make 35MHz receivers with commercially available off the shelf parts. So along as we have access to the 35MHz band, its perfectly achievable to still have working receivers for it. Of course it depends on the market for it, but I would be surprised if there wasn't always a cottage industry around to support 35MHz systems. But at the same time, much is true for 2.4GHz too for the future. Many people in the RC world appear to find 2.4GHz devices as 'black-magic'. This signal somehow magically is received onto a PCB into a little black IC that pumps out the servo signals. The reality is, even though there is more going on, its not rocket science and still pretty simple. The majority of 2.4GHz systems out there use common and pretty simple modulation techniques. Even though the biggest risk on 2.4GHz systems is that certain ICs will become discontinued, it doesn't necessarily mean the system will become dead. As the modulation techniques are pretty standard (for FHSS based systems that usually means the modulation is either FSK or GFSK based), there will be a whole load of replacement RF Chipsets that can do the same job. So even in 25 years, it's entirely plausible that 2.4GHz RC transmitters and receivers will still exist and still be compatible. Incidentally, given how much 2.4GHz stuff is out there commercially (WiFi, Bluetooth, Cordless phones, Microwave ovens, etc, etc, etc), it's not a band that will disappear quickly. Also as we all fly out in the middle of open spaces well away from buildings and other structures (well you should be anyway), even as 2.4GHz gets pretty crowded, there is little risk for us to be blocked out. Just how far can you go before too much 2.4GHz traffic is too much? Well I'd put money on that if you're walking down regents street this time of year, your low powered 2.4GHz Bluetooth headset will still be happily chatting with your phone... Incidentally the 35MHz band is set at a EU level (the spec is detailed in the ETSI document EN 300 220). So its unlikely that we will loose the band anytime soon. Si.

Posted by Glyn R on 07/12/2013 22:34:25: I keep reading these long drawn out frequency discussions. The real trick with modern 2.4ghz Radios is the use of Digital technology. The provision of the GUID based systems is the real advance. The frequency has to be high enough for the frame rate to be practical. Each data packet carries the Globally Unique Identifier the frequency used is not the really clever bit. eh? You realise PCM on 35MHz is digital data right? Adding 16 to 32bits extra hardly will increase the frame rate at all. Even with a GUID if you're transmitting on a very small frequency band that each 35MHz channel uses, if someone else transmits on that same channel you'll still get stamped out... With 2.4GHz its wide enough band to be able to hop and/or spread over a 80MHz frequency range. Of course this wouldn't be possible if you had to keep in a very small space as you do with the 35MHz band (to avoid hitting the older systems). Also having GUID and packet based data transmissions doesn't solve the interference susceptibility issue of the lower frequencies. Here for example is a spectrum anaylser plot between 1MHz and 1000MHz (1GHZ) of a cheap 3v DC motor (commonly used in toys) showing in purple the noise when the dc motor is running and the yellow is the baseline ambient (motor off) state: (remember the scale is in dB's) This is the motor in question: Note how the noise rolls off at the higher frequencies. Even this little low powered motor is a sizable noise source which will cause problems if left next a sensitive receiving RF section. Again remember most 35MHz receivers don't have their RF sections shielded either (unlike modern RF Chipsets such as those used for 2.4GHz with the RF sections in silicon), so will be even more susceptible to noise. Si.

Posted by Erfolg on 07/12/2013 12:14:06: It does seem to me that this is an area where the BMFA would serve its general RC members well by campaigning and actively seeking a band with the width for the sole usage of RC models. We do! Its between 458.5 to 459.5MHz and is reversed especially for model flyers - the old UHF frequency that equipment used to come in. This frequency is commonly used by FPV guys nowadays as its not as polluted as the ~430MHz band (Amateur Radio frequencies and other licence exempt devices) that is often used by the LRS (Long Range Systems). It's not a huge band, but large enough to have a few channels to hop around in and fit a decent modulation system in. Also there are many commercial volume ICs (thanks to keyfobs, temperature sensors, etc) that can tune into that frequency (usually these ICs can tune a whole range between at least 400-500Mhz) so transmitters and receivers don't have to be that expensive either. Staying on the theme of FPV, those that are on here who think they can use 2.4GHz video at the flying field with a 35MHz transmitter will find out quickly its a bad idea. Firstly those poor guys still on DSM2 will find when a model flies near them with a video transmitter with a decent power output will start to have problems. Secondly, you'll find that all the other 2.4GHz RC transmitters that are hopping all over the frequency band will stomp all over your analog video signal! This is why most FPV guys (in the UK) now use 5.8GHz for video and 2.4GHz for control. The other great leap forward that we benefit from on 2.4GHz equipment is the nearly total integration of the RF circuitry into a single IC. That IC contains all the tuning, mixing, demodulation, etc that has been under a laser in the factory to calibrate, tune and match it all directly on the IC's silicon die. As devices produced for the 2.4GHz frequency band as so wide spread and have been for a while - a lot is known on how to produce reliable devices. After all, companies can't afford large returns with faulty goods. Look inside any 35MHz receiver and you'll find its cluttered with chokes, inductors, capacitors and other passive components that have had to be tuned by hand in a factory. As these parts are large and have a lot of mass in them, they have to be physically glued to the PCB to prevent them being destroyed by vibration and shock. So in answer to those who say will 2.4GHz be around in 25 years - it probably will be, however most of your 35MHz receivers won't be! One reason 2.4GHz suffers less interferences from on-board electronics than 35MHz is because most EMF interference (from motors, ESCs, switching contacts, etc, etc) ends up at 1GHz. So 2.4GHz is high enough to be far enough away from this source of interference. The obvious downside is that it is much more Line of Sight than 35MHz - so pretty much anything solid from a distance will block the signal. However for us this isn't a big deal for most of us as its pretty hard to fly behind trees, etc! Even for FPV use, there is the requirement that the model has to be visible by your observer - so again its still LOS. Cheers, Si.

Posted by John Privett on 07/12/2013 11:16:55: I've gone off Spotify recently. For a start there's all the adverts - I say "all" the adverts, there are only a very small number of different ads, so you keep hearing the same ones over and over again and they are somewhat intrusive suddenly popping-up between tracks in what you're listening to. Then they limited the number of times you could listen to a particular track - as mentioned by Steve. But most recently they seem to have dropped that limitiation and now limit you to the number of hours a week (or month?) you listen. Of course I could pay them some money - which is clearly what they're trying to get people to do... I now use Google Music to listen to stuff that I "own" - you upload all your MP3s and they match them against their database and let you listen online from anywhere to what you already have. Of course for stuff I don't own then I'd need to go back to Spotify. Edited By John Privett on 07/12/2013 11:17:44 That time limit has been there for a couple of years now. You tend to only get the warning when you get near the end. Its annoying, especially with the ads - however it is free! For a long time Spotify was making a loss (and I think still is), so they had to be more aggressive to try and turn a profit. The other alternative is that you can often find tracks free on Youtube...

Posted by Steve Hargreaves - Moderator on 07/12/2013 10:06:07: Spotify is certainly good but you can only play tracks a number of times (I think its 5) unless you subscribe which is £10 a month I think.... Its £5 for laptop/desktop use and £10 a month for laptop/desktop/tablet/phone/etc use. If you're on one of the 4G plans on Vodafone you get it included too. £10 a month is like the cost of an album a month. £5 a month is not far off the cost of a monthly issue of RCM&E from the newsagents...

Something that runs Spotify - I.e laptop, iDevice or android and a decent pair of speakers/dock. You can then play pretty much most stuff without having to own it (legally)! Si.

Start with the CoG in the correct location if you're not experienced flying 3D style. As you get confident in the airframe, then start moving the CoG back. Tank is useful in the CoG location as the CoG changes a lot less as the fuel drains. As an aircraft set up in a 3D manor will have the CoG as far back as is possible, removing fuel from the front, moving the CoG back further won't be good... For a 25CC, I personally don't think you need to bother with the extra weight of a dual battery setup. If you do, then I'd just connect them in parallel together. For Li-Fe packs, the voltage discharge curve is very flat and discharges around 6.6v, so you don't need a regulator. Also the maximum full-charged voltage of a Li-Fe pack is less than a 5Cell Ni-Mh pack too. Also 6.6V will give you faster responses than the servos being ran on 5.9V. Watch out for the flat discharge curve on Li-Fe. You can't accurately determine the remaining flying time on voltage. You need to time your flights and then recharge the pack, seeing how many mAh go back in after x minutes. Si.

WinZip was your problem. Not only a pretty naff piece of software by today's standards, its also unnecessary to have installed. Since Windows XP, Windows has inbuilt ZIP file support. Si

Just in case too many people take this seriously, here is what is said on their facebook page... "Ok guys! Some of you were right! The dentidrill isn’t real… However, the Dutch company ixorg (for affordable dental care) is! Check here: **LINK**" Si.

Posted by scott cuppello on 27/10/2013 12:56:11: Which do you reckon is the best platform FPV Raptor, Skywalker 1680, EPP-FPV or a glider (i.e. Phoenix 2000)? Got an AXN clouds flyer as part of a deal of FPV stuff I bought (at a ridiculously cheap price) - but it flies crap imo. Not too bothered about not being foam as I very rarely crash nowday's. Hate trying to launch wings too. Cheers, Si. Thing is that they all have their pro's and con's, Skywalker is probably the better all rounder, especially if you are not keen on wings but then the FPV Raptor is the better glider. Stabilizer makes it academic to a degree in terms of how well they fly but for me either the Skywalker and FPV Raptor have the edge because they are designed for the job, . You could go non-foam like the the Raven UAV airframe (as used by the US Military) but I think you have to be pretty confident with regard flying sites when it comes to composite/balsa hand-launch models, I would expect the Raven to penetrate better and have a better wind tolerance than foam obviously but foam has that all round tolerance to abuse. Cheers scott, something for me to mull over. I didn't know there was a Raven kit about - will have to go investigate. I'm going to give FPV a bit longer on the existing stuff to see how I like it and what I find the most fun (i.e. long range or fast and close). Found my old TwinStar 2 at the back of the garage - I think I'll transplant the gear over to that. I know quite a lot of guys use the Twinstar for FPV (including the flight test boys for their air-to-air footage). Si.